The study of Morphogenesis of HIV particles in various host cells with various isolates and mutant virus strains continues to provide an interesting insight into HIV infection and remains an important tool in correlating biological changes with genetic variation. U gene mutants of HIV demonstrate considerable differences from wild- type virus when examined at 7 days with many cells showing intracytoplasmic immature particles while WT virus shows a few cells with typical mature particles budding off the cell membrane. By day 10, U mutant virus is seen budding from many cells but only a rare mature form is seen. HIV has been shown to replicate in rabbit cells with the production of RT and typical mature particles budding from the cell surface. Several molecular clones of different HIV strains have shown different plaque morphologies when grown in MT-4 cells while little or no difference can be seen when observed in the EM after growth in A3.01, MT-4 or PBL cell cultures. Both rabbits and guinea pigs have been used to raise antibodies against various molecular clones of HIV which can be demonstrated by Western blot analysis. The MT-4 Plaque test has been used to demonstrate recombination between different HIV mutants with defects in different genes.